1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_TTY_LDISC_H
3 #define _LINUX_TTY_LDISC_H
8 * This structure defines the interface between the tty line discipline
9 * implementation and the tty routines. The following routines can be
10 * defined; unless noted otherwise, they are optional, and can be
11 * filled in with a null pointer.
13 * int (*open)(struct tty_struct *);
15 * This function is called when the line discipline is associated
16 * with the tty. The line discipline can use this as an
17 * opportunity to initialize any state needed by the ldisc routines.
19 * void (*close)(struct tty_struct *);
21 * This function is called when the line discipline is being
22 * shutdown, either because the tty is being closed or because
23 * the tty is being changed to use a new line discipline
25 * void (*flush_buffer)(struct tty_struct *tty);
27 * This function instructs the line discipline to clear its
28 * buffers of any input characters it may have queued to be
29 * delivered to the user mode process.
31 * ssize_t (*read)(struct tty_struct * tty, struct file * file,
32 * unsigned char * buf, size_t nr);
34 * This function is called when the user requests to read from
35 * the tty. The line discipline will return whatever characters
36 * it has buffered up for the user. If this function is not
37 * defined, the user will receive an EIO error.
39 * ssize_t (*write)(struct tty_struct * tty, struct file * file,
40 * const unsigned char * buf, size_t nr);
42 * This function is called when the user requests to write to the
43 * tty. The line discipline will deliver the characters to the
44 * low-level tty device for transmission, optionally performing
45 * some processing on the characters first. If this function is
46 * not defined, the user will receive an EIO error.
48 * int (*ioctl)(struct tty_struct * tty, struct file * file,
49 * unsigned int cmd, unsigned long arg);
51 * This function is called when the user requests an ioctl which
52 * is not handled by the tty layer or the low-level tty driver.
53 * It is intended for ioctls which affect line discpline
54 * operation. Note that the search order for ioctls is (1) tty
55 * layer, (2) tty low-level driver, (3) line discpline. So a
56 * low-level driver can "grab" an ioctl request before the line
57 * discpline has a chance to see it.
59 * int (*compat_ioctl)(struct tty_struct * tty, struct file * file,
60 * unsigned int cmd, unsigned long arg);
62 * Process ioctl calls from 32-bit process on 64-bit system
64 * NOTE: only ioctls that are neither "pointer to compatible
65 * structure" nor tty-generic. Something private that takes
66 * an integer or a pointer to wordsize-sensitive structure
67 * belongs here, but most of ldiscs will happily leave
70 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
72 * This function notifies the line discpline that a change has
73 * been made to the termios structure.
75 * int (*poll)(struct tty_struct * tty, struct file * file,
78 * This function is called when a user attempts to select/poll on a
79 * tty device. It is solely the responsibility of the line
80 * discipline to handle poll requests.
82 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
83 * char *fp, int count);
85 * This function is called by the low-level tty driver to send
86 * characters received by the hardware to the line discpline for
87 * processing. <cp> is a pointer to the buffer of input
88 * character received by the device. <fp> is a pointer to a
89 * pointer of flag bytes which indicate whether a character was
90 * received with a parity error, etc. <fp> may be NULL to indicate
91 * all data received is TTY_NORMAL.
93 * void (*write_wakeup)(struct tty_struct *);
95 * This function is called by the low-level tty driver to signal
96 * that line discpline should try to send more characters to the
97 * low-level driver for transmission. If the line discpline does
98 * not have any more data to send, it can just return. If the line
99 * discipline does have some data to send, please arise a tasklet
100 * or workqueue to do the real data transfer. Do not send data in
101 * this hook, it may leads to a deadlock.
103 * int (*hangup)(struct tty_struct *)
105 * Called on a hangup. Tells the discipline that it should
106 * cease I/O to the tty driver. Can sleep. The driver should
107 * seek to perform this action quickly but should wait until
108 * any pending driver I/O is completed.
110 * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
112 * Tells the discipline that the DCD pin has changed its status.
113 * Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
115 * int (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
116 * char *fp, int count);
118 * This function is called by the low-level tty driver to send
119 * characters received by the hardware to the line discpline for
120 * processing. <cp> is a pointer to the buffer of input
121 * character received by the device. <fp> is a pointer to a
122 * pointer of flag bytes which indicate whether a character was
123 * received with a parity error, etc. <fp> may be NULL to indicate
124 * all data received is TTY_NORMAL.
125 * If assigned, prefer this function for automatic flow control.
128 #include <linux/fs.h>
129 #include <linux/wait.h>
130 #include <linux/atomic.h>
131 #include <linux/list.h>
132 #include <linux/lockdep.h>
133 #include <linux/seq_file.h>
136 * the semaphore definition
138 struct ld_semaphore {
140 raw_spinlock_t wait_lock;
141 unsigned int wait_readers;
142 struct list_head read_wait;
143 struct list_head write_wait;
144 #ifdef CONFIG_DEBUG_LOCK_ALLOC
145 struct lockdep_map dep_map;
149 void __init_ldsem(struct ld_semaphore *sem, const char *name,
150 struct lock_class_key *key);
152 #define init_ldsem(sem) \
154 static struct lock_class_key __key; \
156 __init_ldsem((sem), #sem, &__key); \
160 int ldsem_down_read(struct ld_semaphore *sem, long timeout);
161 int ldsem_down_read_trylock(struct ld_semaphore *sem);
162 int ldsem_down_write(struct ld_semaphore *sem, long timeout);
163 int ldsem_down_write_trylock(struct ld_semaphore *sem);
164 void ldsem_up_read(struct ld_semaphore *sem);
165 void ldsem_up_write(struct ld_semaphore *sem);
167 #ifdef CONFIG_DEBUG_LOCK_ALLOC
168 int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
170 int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
173 # define ldsem_down_read_nested(sem, subclass, timeout) \
174 ldsem_down_read(sem, timeout)
175 # define ldsem_down_write_nested(sem, subclass, timeout) \
176 ldsem_down_write(sem, timeout)
180 struct tty_ldisc_ops {
185 * The following routines are called from above.
187 int (*open)(struct tty_struct *);
188 void (*close)(struct tty_struct *);
189 void (*flush_buffer)(struct tty_struct *tty);
190 ssize_t (*read)(struct tty_struct *tty, struct file *file,
191 unsigned char *buf, size_t nr,
192 void **cookie, unsigned long offset);
193 ssize_t (*write)(struct tty_struct *tty, struct file *file,
194 const unsigned char *buf, size_t nr);
195 int (*ioctl)(struct tty_struct *tty, struct file *file,
196 unsigned int cmd, unsigned long arg);
197 int (*compat_ioctl)(struct tty_struct *tty, struct file *file,
198 unsigned int cmd, unsigned long arg);
199 void (*set_termios)(struct tty_struct *tty, struct ktermios *old);
200 __poll_t (*poll)(struct tty_struct *, struct file *,
201 struct poll_table_struct *);
202 void (*hangup)(struct tty_struct *tty);
205 * The following routines are called from below.
207 void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
208 const char *fp, int count);
209 void (*write_wakeup)(struct tty_struct *);
210 void (*dcd_change)(struct tty_struct *, unsigned int);
211 int (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
212 const char *fp, int count);
214 struct module *owner;
218 struct tty_ldisc_ops *ops;
219 struct tty_struct *tty;
222 #define MODULE_ALIAS_LDISC(ldisc) \
223 MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
225 extern const struct seq_operations tty_ldiscs_seq_ops;
227 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *);
228 void tty_ldisc_deref(struct tty_ldisc *);
229 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *);
231 void tty_ldisc_flush(struct tty_struct *tty);
233 int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc);
234 void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc);
235 int tty_set_ldisc(struct tty_struct *tty, int disc);
237 #endif /* _LINUX_TTY_LDISC_H */